This invention is directed to the laser deposition of crystalline films of silicon carbide from elemental targets involving carbon, and optionally silicon, onto silicon, which films are preferably epitaxial.
The most frequently used method for the growth of crystalline silicon carbide (SIC) films is that of chemical vapor deposition (CVD) from a stream of carbon and silicon containing molecules, e.g., hydrocarbons and silane, respectively. CVD depositions are usually carried out in a hydrogen atmosphere and often, for silicon carbide film formation, the substrate for film growth is a single crystal Si wafer. Usually the silicon carbide CVD deposition is initiated with a carbonization step which involves first growing a thin SiC film by reacting at high temperature only the hydrocarbon with the Si substrate. Amorphous or polycrystalline SiC films can also be grown by ion sputtering of SiC targets.
In a number of experiments where Si has been subjected to bombardment by energetic C.sup.+ ions formation of dispersed SiC crystallites in a thin layer of non-stoichiometric Si.sub.x Cl.sub.1-x near the surface has been reported. It has also been reported that bombardment of Si with a large fluence of 100 keV C.sup.+ ions will produce a disordered C-Si mixture which upon subsequent high temperature annealing will transform into polycrystalline SiC.
It has been disclosed in "Preparation of Oriented Silicon Carbide Films by Laser Ablation of Ceramic Silicon Carbide Targets", L. Rimai, R. Ager, E. M. Logothetis, W. H. Weber and J. Hangas, Appl. Phys. Lett. 59 (18), 2266, (1991) that crystalline SiC films can be grown on Si wafers by pulsed laser ablation of a ceramic SiC target and that under suitable conditions these films exhibit a substantial degree of epitaxial orientation. One disadvantage of this procedure is the requirement of a ceramic SiC target as the source of material. Such targets usually contain additives needed for their preparation, which will get transferred as impurities to the growing film. The ablation rate for such targets is relatively low, resulting in slow film growth. The present invention method overcomes these deficiencies of prior art methods by using as source of carbon atoms for the SiC film a plume generated by laser ablation of pure elemental carbon target and as a source of silicon atoms either the silicon substrate itself or a laser ablation plume from a pure silicon target.